Film formation apparatus

ABSTRACT

A metal atomic layer and an oxygen atomic layer are formed in this order by ALD, followed by rapid heating through RTA (Rapid Thermal Annealing). This cycle of steps is repeated to form a high dielectric constant film.

BACKGROUND OF THE INVENTION

This is a U.S. national stage of application No. PCT/JP2004/004076,filed on 24 Mar. 2004. Priority under 35 U.S.C. §119(a) and 35 U.S.C.§365(b) is claimed from Japanese Application No. 2003-083692, filed 25Mar. 2003, the disclosure of which is also incorporated herein byreference.

1. Field of the Invention

The invention relates to a deposition system which is capable of forminga metal compound thin film by atomic layer.

2. Description of the Related Art

In recent years, intensive studies have been made on the use of highdielectric constant thin films, called high-k, as materials forconstituting semiconductor devices. High dielectric constant thin filmsare formed by such methods as CVD (Chemical Vapor Deposition), ALD(Atomic layer deposition), and sputtering. Of these, ALD is a method forforming a thin film by cyclic supply of reactants for chemicalsubstitution, not by thermal decomposition. This method provides asuperior capability for split-level coating as compared to physicaldeposition methods such as sputtering, and also allows low-temperatureprocesses. It is thus considered as a promising method for forming ahigh dielectric constant thin film to constitute a semiconductor device(for example, see Japanese Laid-Open Patent Applications 2001-152339,2001-254181, and 2002-314072).

A system for conducting this ALD-based deposition appears in JapaneseLaid-Open Patent Application 2001-254181. This deposition system is onefor achieving the process of supplying a first source gas to a substrateplaced in a deposition chamber, purging this source gas, and thensupplying a second source gas thereto. Switching the source gases andthe purge gas alternately at speed allows deposition through theforegoing process, whereby atomic layers can be deposited layer bylayer.

Now, Japanese Laid-Open Patent Application 2002-314072 (FIG. 8)describes a deposition system which has a chamber for performingdeposition processing and a chamber for performing preprocessingseparately. FIG. 14 is a diagram schematically showing the structure ofthis ALD system. The same document describes that when the ALD systemdeposits Al₂O₃ on a silicon substrate, terminating hydrogen on thesilicon surface shall be desorbed. For example, this hydrogen desorptionprocess is performed in an atmosphere of 400° C. or above intemperature, whereas Al₂O₃ is deposited at around 300° C. When theseprocesses are performed continuously in an ordinary ALD system, thesample must be once raised to 400° C. or above in temperature for thesake of the hydrogen desorption process, and then the deposition isperformed after a wait until the sample temperature falls to around 300°C. Then, performing the series of operations wafer by wafer increasesthe number of processes of the ALD system, thereby making the cost ofthe semiconductor device higher.

The deposition system shown in FIG. 14 is to address this problem. TheALD system has a sample introduction chamber 13 which accommodatesto-be-processed and processed samples, a reaction chamber 12 wheredepositing a predetermined film on a sample is carried out, and aconveyor system which conveys the samples in succession. Aside fromthese, the ALD system is also provided with a hydrogen desorptionchamber 11 which performs the hydrogen desorption process. In thehydrogen desorption chamber 11, the hydrogen desorption process iscarried out by using a heating lamp 16. This configuration allows thehydrogen desorption process and the deposition of the dielectric film,having different processing temperatures, to be performed continuously.Because of the provision of the respective chambers for performing thedeposition processing and the preprocessing, it is possible to performthe processes continuously without waiting for the temperature tosettle. Then, it has been concluded that the number of processes of thesemiconductor device can be decreased to reduce the manufacturing costof the semiconductor device.

Any of the deposition systems for performing such ALD-based depositionis basically configured so that a source gas and a purge gas aresupplied alternately. Hereinafter, a typical ALD deposition process tobe achieved by these deposition systems will be described with referenceto FIG. 1. Here, the description will deal with the case of an aluminumoxide film.

Initially, a substrate is placed in the reactive chamber, and then afilm material A is supplied to the surface of the substrate. Here,trimethyl aluminum (Al(CH₃)₃; referred to as “TMA”) is supplied (S101).

Next, the material A is exhausted from the reaction chamber by inactivegas purging (S102). Next, a reactive gas is supplied to the reactionchamber (S103). The reactive gas may be oxygen, water vapor, or thelike. As a result, an oxygen atomic layer is formed on the atomic layermade of the material A. To remove resulting by-products and the reactivegas hanging in the vapor phase, inactive gas purging is then performedto exhaust the air (S104).

The foregoing steps S101 to S104 are repeated to form a high dielectricconstant thin film. Subsequently, whether a predetermined thickness isreached or not is checked by a thickness measuring device which isarranged on the deposition system (S107). If it is confirmed that thepredetermined thickness is reached (Yes at S107), then thermal annealingis performed for the sake of film refining processing (S108). Thisthermal annealing is performed after the completion of the layerformation (Japanese Laid-Open Patent Application No. 2001-152339,paragraph 0047). This completes the deposition steps.

In such a deposition process, however, impurities resulting from thematerials used in the ALD have sometimes remained in the high dielectricconstant thin film or induced film defects. In this respect, descriptionwill be given with reference to FIGS. 2A and 2B. FIGS. 2A and 2B areschematic diagrams showing the layer structure of a high dielectricconstant thin film formed by the steps of FIG. 1. FIGS. 2A and 2Bcorrespond to the states before and after the film refining processingby the thermal annealing shown in S108 of FIG. 1, respectively.

Before the thermal annealing, as shown in FIG. 2A, impurities aredistributed throughout the high dielectric constant thin film. After theannealing, impurities are removed from the entire film. The film is alsodensified. Nevertheless, in the lower areas of the high dielectricconstant thin film or near the substrate in particular, impurities tendto be removed insufficiently and remain intact. In addition, since metaloxides are typically prone to crystallization, the film can be partiallycrystallized in the annealed state of FIG. 2B. The residual impuritiesand the film crystallization described above may contribute todeterioration in the characteristics of the device that contains thehigh dielectric constant thin film. For example, when the highdielectric constant thin film is applied to the gate insulating film ofa transistor, it may cause an increase in leak current, deviations inthreshold characteristics, etc.

To solve these problems, it is desired to adopt a deposition method thatnot only supplies the source gases and the purge gas alternately butalso exercises control of higher sophistication on the film quality. Toachieve such a new deposition method, the deposition system itself mustalso be sophisticated in function.

Related Art List

JPA laid open 2001-152339

JPA laid open 2001-254181

JPA laid open 2002-314072 (FIG. 8)

SUMMARY OF THE INVENTION

The present invention has been achieved in view of the foregoingproblems. It is thus an object of the present invention to provide adeposition system which suppresses impurity contamination and filmdefects so that a thin film of favorable quality is obtained stably byALD. Another object of the present invention is to provide a depositionsystem which is capable of introducing a different type of componentinto the thin film in a desired distribution.

The present invention provides a deposition system which supplies asource gas and a purge gas alternately for deposition, comprising: adeposition chamber; a substrate holding unit which holds a substrate inthe deposition chamber; a source gas supply unit which supplies thesource gas to the deposition chamber; a reactive gas supply unit whichsupplies a reactive gas to the deposition chamber; a purge gas supplyunit which supplies the purge gas to the deposition chamber; an exhaustunit which exhausts the source gas, the reactive gas, and the purge gasfrom the deposition chamber; a first heating unit which heats thesubstrate arranged in the deposition chamber to maintain the same to apredetermined temperature; and a second heating unit which heats thesubstrate arranged in the deposition chamber rapidly.

In the present invention, the “reactive gas” refers to a gas that reactswith a metal to form a metal oxide or a metal nitride. The depositionsystem according to the present invention has the first and secondheating units which heat the substrate arranged in the depositionchamber. The first heating unit can be used to maintain the substrate ata deposition temperature for depositing an atomic layer, and the secondheating unit can be used to heat the substrate rapidly. It is thereforepossible to perform both an atomic layer deposition step and anannealing step in the same deposition chamber without taking out thesubstrate. The two steps can also be switched quickly for deposition.Specifically, it is possible to achieve the deposition process offorming a layer by atomic layer deposition, performing annealing, andforming a layer again.

When the layer forming step is suspended to interpose annealing,impurities mixed in the layer and defects of the layer can be removedsufficiently. The film can also be densified. Moreover, in the annealingstep, an annealing gas such as ammonia can be introduced to form anitrogen-introduced layer or the like inside the thin film freelythrough annealing. With a conventional deposition system, the depositedsubstrate has been taken out of the deposition system and loaded intoanother system for annealing. In contrast, according to the system ofthe present invention, the atomic layer and the annealing can beperformed in the same deposition system. The deposition processdescribed above can thus be achieved stably.

In the present invention, the source gas, the reactive gas, or the purgegas may be introduced in a direction parallel to the surface of thesubstrate. For example, when the system is configured to introduce thepurge gas in a direction-parallel to the substrate, the surface of thesubstrate can be supplied with those gases efficiently so that a thinfilm of favorable quality is obtained stably.

In the present invention, the first heating unit and the second heatingunit may be opposed to each other with the substrate interposedtherebetween, so that the first heating unit heats the substrate fromthe backside and the second heating unit heats the substrate from thesurface. This allows efficient heating by both the heating units.Incidentally, in the present invention, the surface of the substraterefers to the side to be subjected to deposition.

In the present invention, the deposition system may further comprise anannealing gas introducing unit which introduces an annealing gas to thedeposition chamber. This allows the process of forming anitrogen-introduced layer or the like in a desired position inside thethin film through annealing as described above. In addition, an oxidantgas, a reductant gas, or the like can be introduced as the annealing gasduring annealing, whereby impurities can be removed efficiently.

In the present invention, the second heating unit may be an RTP (RapidThermal Processing) unit such as an infrared lamp, a laser annealingunit, and a flashing unit. In this case, the rapid heating of thesubstrate can be conducted stably, so that the process of repeating theatomic layer deposition and the annealing in succession can be conductedstably.

The second heating unit may be arranged outside the deposition chamber.This can effectively suppress contamination of the second heating unitwith the source gas, the reactive gas, and the like.

The first heating unit may be a heater formed on a substrate holdingsurface of the substrate holding unit, for example. This makes itpossible to heat the backside of the substrate by heat conduction orradiation. The substrate can thus be maintained at the depositiontemperature stably.

In the present invention, the configuration capable of purging quickerthan in conventional systems allows the substrate temperature to becooled rapidly. After annealing, it is thus possible to cool thesubstrate rapidly and switch to the next atomic layer deposition stepspeedily. Consequently, both the deposition and the annealing can beperformed in the same deposition chamber. This achieves a depositionsystem which suitably suppresses impurity contamination and filmdefects. Moreover, since the process of forming a nitrogen-introducedlayer or the like in a desired position inside the thin film throughannealing becomes feasible, a different type of component can beintroduced into the thin film in a desired distribution withreliability. This makes it possible to form a high-quality film having adesired component distribution stably.

In the present invention, the substrate holding unit may have a movingmechanism which moves the substrate in position so that the distancebetween the substrate and the second heating unit can be adjusted by anoperation from outside the deposition chamber without opening thedeposition chamber. A high-flow purge gas supply unit and acorresponding exhaust unit may also be provided so that the rapidheating and rapid cooling of the substrate can be performed moresmoothly.

In the present invention, the deposition system may further comprise anannealing gas introducing unit which introduces an annealing gas intothe deposition chamber. When the substrate is put closer to the secondheating unit by the moving mechanism, the substrate or the substrateholding unit may section the deposition chamber into a first chamberhaving the annealing gas introducing unit and a second chamber havingthe source gas supply unit and the reactive gas supply unit so that thesurface of the substrate is exposed to the first chamber. In this case,the annealing is performed in part of the internal space of thedeposition chamber. This further improves the temperaturecontrollability in the process of rapid heating. Moreover, inintroducing the annealing gas into the film, it is possible to controlthe amount of introduction with high precision. Furthermore, at the timeof annealing, the substrate need not be moved from the depositionchamber to a separate annealing chamber. The operations from thedeposition to the annealing can be performed continuously in thedeposition chamber.

In the foregoing configuration, the source gas supply unit and thereactive gas supply unit can be arranged outside the small chambers forthe sake of an improvement to the durability of the deposition system.When the annealing gas is mixed with the source gas or the reactive gas,there may occur a corrosive gas which sometimes corrodes the inner wallsof the deposition chamber. The foregoing configuration can thus beadopted to suppress the production of such a corrosive gas, therebyimproving the durability of the deposition chamber.

The first and second chambers may be formed inside the depositionchamber in various possible modes.

For example, the substrate holding unit and the inner walls of thedeposition chamber may form a first chamber of enclosed structure whenthe substrate is put closer to the second heating unit. This simpleconfiguration can form the small chambers inside the deposition chambereasily, and allows more efficient heating by the second heating unit.

Alternatively, a partition member may be arranged inside the depositionchamber. When the substrate is put closer to the second heating unit bythe moving mechanism, the substrate or the substrate holding unit may becombined with the partition member to form a division wall inside thedeposition chamber, thereby forming the first and second chambers. Thiscan suppress the flow of the annealing gas into the second chamber,whereby corrosion of the inner walls of the deposition chamber issuppressed with reliability. Since the flow of the reactive gas into thefirst chamber is also suppressed, it is possible to suppress chemicalreactions other than intended during annealing.

The deposition system of the present invention may have a control unitwhich controls the operation of the second heating unit and the movingmechanism. The control unit may be configured to start heating thesubstrate by using the second heating unit after the substrate is putcloser to the second heating unit by the moving mechanism. This makes itpossible to heat the substrate even more efficiently.

The deposition system of the present invention may further comprise: anannealing gas introducing unit which introduces an annealing gas to thedeposition chamber; and a control unit which controls the operation ofthe second heating unit, the annealing gas introducing unit, and themoving mechanism. The control unit may be configured to start heatingthe substrate by using the second heating unit and introduce theannealing gas to the deposition chamber from the annealing gasintroducing unit when the substrate is put closer to the second heatingunit by the moving mechanism. This makes it possible to form ahigh-quality film with still higher reliability at speed.

In the deposition system of the present invention, the exhaust unit mayalso be controlled by the control unit so that it can exhaust air fromthe entire deposition chamber when the substrate is put away from thesecond heating unit by the moving mechanism. Consequently, the entiredeposition chamber including the area that makes the small chamber whenthe substrate is put closer to the second heating unit can be exhaustedsimultaneously. This makes it possible to perform gas replacement andcooling inside the deposition chamber with reliability at higher speed.

The deposition system of the present invention is suitably used to forma metal compound layer made of a high dielectric constant materialso-called high-k. Here, the thin film may have a dielectric constant kof 8 or higher, for example. The metal compound layer may contain one ormore elements selected from the group consisting of Hf, Zr, Al, La, Y,Si, Ba, Sr, Ti, Pb, Bi, Ta, Nb, and Mn. Among these, any of Hf, Zr, Al,La, and Y is particularly preferably contained. This can provide astable film having a high dielectric constant.

Specifically, the deposition system can suitably manufacture a film of acompound expressed by the following general formula:M_(y)N_(1-x)O_(x),where x is a number ranging from 0 to 1, and y is a number higher than 0but no higher than 1. Here, M represents one or more metal elements.Specific examples of the metal elements include the ones mentionedabove.

Concrete examples of the compound expressed by the foregoing generalformula include: metal oxides such as Al₂O₃, ZrO₂, HfO₂, Ta₂O₅, Nb₂O₅,CeO₂, Y₂O₃, IrO₂, SrTiO₃, PbTiO₃, SrRuO₃, CaRuO₃, (Ba,Sr)TiO₃,Pb(Zr,Ti)O₃, (Pb,La) (Zr,Ti)O₃, (Sr,Ca)RuO₃, and (Ba,Sr)RuO₃;oxynitrides formed by introducing nitrogen into the foregoing metaloxides; and metal nitrides such as AlN and Hf₃N₄. High dielectricconstant films made of high dielectric constant materials havingrelative permittivities of 10 and above are particularly preferable.Such films may be suitably used for the gate insulating film of a MIS(Metal Insulator Semiconductor) type transistor or the capacitive filmof a capacitor.

According to the deposition system of the present invention, it ispossible to perform the steps of depositing an atomic layer, performingthe annealing in an atmosphere containing a nitrogen compound gas, andthen depositing another atomic layer continuously without taking thesubstrate out of the deposition chamber. Through these steps, a metalnitride layer or metal oxynitride layer can be introduced into anarbitrary position in the metal compound layer of a high dielectricconstant material. In general, high dielectric constant films made ofmetal oxide layers are high in insulation capability, whereas they havea propensity toward crystallization and to pass leak currents easily.When nitrogen is introduced thereto, the crystallization temperatures ofthe layers increase to enhance the film quality and make it harder topass leak currents. According to the present invention, such films canbe formed stably with excellent controllability.

As described above, according to the present invention, impuritycontamination and film defects can be suppressed to obtain a highdielectric constant thin film of favorable quality stably by ALD. It isalso possible to introduce a different type of element such as nitrogeninto the entire high dielectric constant thin film in a desireddistribution.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing objects and other objects, features, and advantages of theinvention will become more apparent from the following description ofpreferred embodiments when read in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a flowchart for explaining conventional typical steps forforming a high dielectric constant thin film by ALD;

FIGS. 2A and 2B are schematic diagrams showing the layer structure of ahigh dielectric constant thin film formed by the steps of FIG. 1;

FIG. 3 is a diagram showing the configuration of a deposition systemaccording to an embodiment;

FIG. 4 is a diagram showing the configuration of the deposition systemaccording to the embodiment;

FIG. 5 is a flowchart for explaining the steps for forming a highdielectric constant thin film according to the embodiment;

FIGS. 6A to 6D are schematic diagrams showing the layer structure of thehigh dielectric constant thin film formed by the steps of FIG. 5;

FIGS. 7A and 7B are diagrams showing the sequence of gas supply andwafer cooling;

FIG. 8 is a diagram showing the configuration of the deposition systemaccording to another embodiment;

FIG. 9 is a diagram showing the configuration of the deposition systemaccording to the embodiment;

FIG. 10 is a diagram showing the configuration of the deposition systemaccording to another embodiment;

FIG. 11 is a diagram showing the configuration of the deposition systemaccording to the embodiment;

FIG. 12 is a diagram showing the sequence of gas supply and wafertemperature control in the method of forming a high dielectric constantthin film according to an embodiment;

FIG. 13 is a diagram showing the sequence of gas supply and wafertemperature control in the method of forming a high dielectric constantthin film according to another embodiment;

FIG. 14 is a diagram showing the configuration of a conventionaldeposition system;

FIG. 15 is a diagram for explaining a method of process management inthe deposition system according to an embodiment; and

FIG. 16 is a diagram for explaining another method of process managementin the deposition system according to the embodiment.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

FIG. 3 is a diagram showing the configuration of a deposition systemaccording to the present embodiment. In the shown deposition system 200,an Si wafer 206 is placed on a stage 268 which is provided with a heater208. The stage 268 is supported by a supporting unit 214. Inlets for areactive gas (H₂O), a source gas of a metal compound, and a purge gasare formed in the system. An outlet for exhausting the gases out of thedeposition chamber is formed in the right side of the system. A quartzcover 258 is provided in order to prevent gas components from adheringto the stage 268 and the supporting unit 214.

An RTP unit 202 is installed over a quartz window 204 which is formed ina wall of the deposition chamber 216. The Si wafer 206 is maintained ata predetermined temperature by the heater 208 during deposition, and isheated rapidly by the RTP unit 202. That is, the heater 208 is a heatsource for maintaining the Si wafer 206 at a predetermined depositiontemperature, or the deposition temperature shown in FIG. 7B to be seenlater, during deposition. The RTP unit 202 is a heat source for reachingthe annealing temperature during thermal annealing. The RTP unit 202 maybe a rapid thermal processing unit such as an infrared lamp, a laserannealing unit, and a flashing unit.

In this system, the deposition chamber 216 is given a volume ratiosignificantly smaller than heretofore with respect to the flow rate ofthe purge gas. The interior of the deposition chamber 216 can thus bereplaced with the cooling purge gas of high flow rate in a short time.Consequently, it becomes possible to lower the temperature inside thedeposition chamber 216 sharply. Moreover, the RTP unit 202 attached tothe deposition system 200 allows a quick rise in temperature.

FIG. 4 is a diagram showing the configuration of the deposition system200 in more details. Here, the configuration of the piping connected tothe deposition chamber 216 is shown. Valves 238 and 240 are formed on asource gas supply pipe 222 for supplying the source gas of a metalcompound thin film to the deposition chamber 216. The source gas supplypipe 222 is connected with a tank, a cylinder, or the like that containsthe source gas. A purge gas supply pipe 224 communicating with thesource gas supply pipe 222 is provided with a valve 242. Incidentally,the source gas may be the material of a high dielectric constant film(high-k material). In this case, a metal compound thin film having ahigh dielectric constant can be suitably formed on the surface of the Siwafer 206.

Valves 244 and 246 are formed on a reactive gas supply pipe 226 forsupplying the reactive gas (H₂O) to the deposition chamber 216. Thereactive gas supply pipe 226 is connected with a tank, a cylinder, orthe like that contains the reactive gas. A purge gas supply pipe 228communicating with the reactive gas supply pipe 226 is provided with avalve 248. A purge gas supply pipe 230 for introducing a large amount ofcooling purge gas into the deposition chamber 216 is provided with avalve 250.

In the deposition system 200, the source gas supply pipe 222, the purgegas supply pipe 224, the reactive gas supply pipe 226, the purge gassupply pipe 228, and the purge gas supply pipe 230 may be made of anymaterials as long as they have resistance against the gas componentsflowing through the respective pipes and against the temperaturesthereof. For example, stainless steel pipes may be used. The valves 238to 250 may be configured so that they are opened and closed under thecontrol of a not-shown computer, for example.

The walls of the deposition chamber 216 may be made of any material aslong as it has resistance against heat, oxidants, and reductants. Forexample, stainless steel or other metals may be used. A heat insulatingcover 210 may be arranged on the external walls of the depositionchamber 216. The heat insulating cover 210 may be made of glass wool,for example.

Now, the method of manufacturing a thin film by using the depositionsystem 200 will be described with reference to FIG. 5. Initially, an Siwafer 206 is placed in the deposition chamber 216. Then, a film materialA is introduced from the source gas supply pipe 222 into the depositionchamber 216 and is supplied to the surface of the Si wafer 206 (S101).Here, the valves 238 and 240 are open, and the valve 242 is closed. Thematerial A is a metal compound. For example, trimethyl aluminum (TMA) isused to form an aluminum oxide layer. To deposit ZrO₂, such a source gasas zirconium chloride (ZrCl₄) is selected and used as appropriate. Todeposit HfO₂, such source gases as hafnium chloride (HfCl₄) and hafniumpropoxide (Hf(iOPr) ₄) may be used. During deposition, the temperatureof the Si wafer 206 is adjusted by the heater 208. The temperature ofthe heater 208 is measured by a temperature measuring unit 256.

Subsequently, purging is performed by using an inactive gas, so that thematerial A is exhausted (S102). Here, the valve 238 is closed and thevalve 242 is opened to supply the purge gas from the purge gas supplypipe 224. This makes it possible to eliminate the source gas remainingin the source gas supply pipe 222.

Next, the reactive gas is supplied from the reactive gas supply pipe 226to the deposition chamber 216 (S103). Here, the valves 244 and 246 areopened, and the valve 248 is closed. The examples of the reactive gasinclude H₂O, O₃, O₂, N₂O, NH₃, and NO. Consequently, an oxygen atomiclayer is formed on the atomic layer made of the material A. To removethe reactive gas and resulting by-products hanging in the vapor phase,inactive gas purging is performed to exhaust the air (S104). Here, thevalve 244 is closed and the valve 248 is opened to introduce the purgegas from the purge gas supply pipe 228. Consequently, the reactive gasin the reactive gas supply pipe 226 can be removed suitably.

Subsequently, thermal annealing is conducted for the sake of impurityremoval processing and film reforming processing (S105, S106). Thisannealing is carried out inside the deposition chamber 216 where theforegoing steps S101 to S105 are performed. That is, the Si wafer 206 isthermally annealed simply without being taken out of the depositionchamber 216. The annealing temperature is set as appropriate accordingto the film materials etc. Typically, an appropriate temperature isselected from the range of 400° C. to 1000° C. Incidentally, the heatingtemperature by the RTP unit 202 is adjusted based on the temperaturemeasured by a radiation thermometer 254.

The cycle consisting of the foregoing steps S101 to S106 is repeated tostack atomic layers. Subsequently, whether a predetermined thickness isreached or not is checked by a thickness measuring device (not shown)which is arranged on the deposition system 200 (S107). If thepredetermined thickness is not reached (No at S107), the annealed Siwafer 206 is cooled rapidly to repeat the steps from S101.

The rapid cooling of the deposition chamber 216 is effected by supplyingthe purge gas from the purge gas supply pipe 230 and exhausting the airfrom the outlet as well. This can cool the Si wafer 206 efficiently, sothat the processing can be shifted from step S106 to S101 promptly. AtS107, if it is confirmed that the predetermined thickness is reached(Yes at S107), the atomic layer forming steps are ended. Then, annealingis performed for the sake of film refining processing (S108).

FIGS. 6A to 6D are diagrams schematically showing the process how atomiclayers are stacked by the steps of FIG. 5. FIG. 6A shows the state afterthe execution of the steps S101 to S104 in FIG. 5. Metal atoms, oxygenatoms, and impurities are deposited on the substrate. FIG. 6B shows thestate after the execution of the steps S105 and S106 in FIG. 5. Thethermal annealing has removed the impurities from the film. FIGS. 6C and6D show the layer structure at respective stages after the foregoingsteps are repeated. The thermal annealing provides the densified layerstructure having little impurities as shown in FIG. 6D.

The foregoing process will now be described further in terms of gassupply and a temperature profile. FIG. 7A is a diagram showing thesequence of gas supply and wafer cooling. Initially, the source gas formaterial is supplied (sequence 1). Next, the reactive gas is supplied(sequence 2). Subsequently, annealing is performed for the sake ofimpurity removal and film densification (sequence 3). Then, the Si wafer206 is cooled (sequence 4) to complete a single cycle of depositionsteps. This cycle is performed a plurality of times to form the highdielectric constant thin film.

FIG. 7B is a diagram showing the relationship among the cycle, thetemperature of the Si wafer 206, and the gas flow rate. The numeralsgiven to the deposition sequence of FIG. 7B correspond to those of FIG.7A. While the deposition sequences 1 and 2 are executed, the wafertemperature is maintained at a relatively low temperature. From thestate after the completion of the deposition sequence 2, the temperatureis increased rapidly by the RTP unit 202. The annealing is thusperformed in the deposition sequence 3 (impurity removal, anddensification). In the meantime, the wafer temperature is maintainedhigh. The annealing is conducted by using an infrared lamp or laserannealing, and completed in a short time. Subsequently, the Si wafer 206is cooled in the sequence 4. To achieve this process, it is ofimportance to increase the temperature of the Si wafer 206 rapidly andperform annealing without taking the Si wafer 206 out of the depositionchamber 216, and to lower the temperature of the Si wafer 206 sharply soas not to hinder the next deposition step. These requirements have beenunattainable by conventional deposition systems. Since the depositionsystem 200 has the heater 208 and the RTP unit 202, it is possible toexercise high speed heating by the RTP unit 202 during annealing.Moreover, since the speed of introduction of the purge gas from thepurge gas supply pipe 230 and the speed of exhaust of the purge gas fromthe outlet are significantly higher than in conventional systems, rapidcooling is also possible. This eliminates the need for the Si wafer 206to be transported from the chamber for deposition to a chamber forannealing as in the conventional systems. As above, according to thedeposition system 200, it is possible to increase the temperature of theSi wafer 206 and cool the same rapidly. Then, the deposition and theannealing both can be achieved in the deposition chamber 216. Thisallows the process of performing deposition, annealing, and depositionagain. Impurity contamination and film defects can thus be suppressedsuitably, so that a thin film of favorable quality can be obtainedstably. In addition, since the deposition and the annealing can beperformed at desired timing, it is possible to introduce different typesof components into the thin film in a desired distribution.

Second Embodiment

FIGS. 8 and 9 are diagrams showing the configuration of a depositionsystem according to the present embodiment. FIG. 8 shows the state wherea supporting unit 214 of the deposition system 260 is lifted. FIG. 9shows the state where the supporting unit 214 is lowered. In thedeposition system 260, the Si wafer 206 is placed on the supporting unit214 which has a moving mechanism 212. The Si wafer 206 can thus bedisplaced in the height direction. For example, the moving mechanism 212may be configured to extend and contract the supporting unit 214electrically. The moving mechanism 212 for changing the height of thesupporting unit 214 according to an operation on a switch arrangedoutside the deposition chamber 216 may be formed inside the supportingunit 214.

For rapid heating, the deposition system 260 moves the Si wafer 206upward to approach the RTP unit 202 as shown in FIG. 8. For rapidcooling, on the other hand, the Si wafer 206 is moved downward to drawapart from the RTP unit 202 as shown in FIG. 9. Besides, the interior ofthe chamber is purged by a large amount of purge gas introduced from thepurge gas supply pipe 230. In the deposition system 260, the outlet isformed in the upper part of the deposition chamber 216. The stage 268and the gas supply channels have the same structures as in FIG. 6.

The deposition system 260 is configured so as to be capable of adjustingthe distance between the RTP unit 202 and the Si wafer 206. In addition,the outlet lies in the upper part of the deposition chamber 216. Thisallows prompt gas exchange and temperature adjustment, thereby achievinga structure better suited for rapid heating and rapid cooling. At thetime of heating, the distance between the RTP unit 202 and the Si wafer206 is selected as appropriate according to such factors as the outputof the RTP unit 202.

Third Embodiment

FIGS. 10 and 11 are diagrams showing the configuration of a depositionsystem according to the present embodiment. FIG. 10 shows the statewhere a supporting unit 214 of the deposition system 262 is lifted. FIG.11 shows the state where the supporting unit 214 is lowered. In thisdeposition system 262, the Si wafer 206 is placed on the supporting unit214 which has a moving mechanism 212 as is the case with the depositionsystem 260 described in the second embodiment. The Si wafer 206 can thusbe displaced in the height direction. Moreover, in the deposition system262 of the present embodiment, a partition plate 264 is arranged at aposition lower than the inlet of the annealing gas and higher than theinlets of the other gases. An outlet for exhausting the source gas andthe reactive gas is formed in the lower part of the deposition chamber216. Besides, an annealing gas outlet 266 for exhausting the purge gasor the annealing gas is formed in the upper part of the depositionchamber 216. Here, the annealing gas outlet lies above the partitionplate 264. The stage 268 and the gas supply channels have the samestructures as in FIG. 4.

The Si wafer 206 is moved by the moving mechanism 212 so that the quartzcover 258, the supporting unit 214, the Si wafer 206 on the supportingunit 214, and the partition plate 264 form a division wall together.This forms two small chambers inside the deposition chamber 216. In aconventional deposition system, the interior of the deposition chamberis intended for deposition alone. For annealing, the Si wafer 206 mustbe taken out of the system and transported to a separate annealingsystem. Otherwise, even when the Si wafer 206 is not taken out of thedeposition system 260, it must be transported to an annealing chamberseparate from the deposition chamber. In contrast, in the depositionsystem 262, the partition plate 264 suitably forms a small chamber forannealing inside the deposition chamber 216. This configuration makes itpossible to heat and cool the Si wafer 206 even more efficiently.

In performing thermal annealing on the Si wafer 206, as shown in FIG.10, the moving mechanism 212 is adjusted so that the sides of thepartition plate 264 come into contact with the sides of the Si wafer 206or the sides of the stage 268. As a result, the annealing gas is onlysupplied to and exhausted from the small chamber above the partitionplate 264 while the flow of the annealing gas into the chamber below thepartition plate 264 is blocked. Consequently, erosion of the inner wallsof the deposition chamber 216, ascribable to contact of the annealinggas and the reactive gas inside the deposition chamber 216, can besuppressed suitably. For example, suppose that a reductant gas NH₃ isselected as the annealing gas, and an oxidant gas H₂O is selected as thereactive gas. If the two gases make contact with each other in thedeposition chamber 216, they may promote erosion of the inner walls ofthe deposition chamber 216. This can be suppressed, however, by theprovision of the partition plate 264. The same holds when an oxidant gasis selected as the annealing gas and a reductant gas is selected as thereactive gas. In addition, it is possible to suppress a drop in thedegree of vacuum ascribable to the presence of the reactive gas (such asH₂O) above the partition plate 264. Besides, the small chamber above thepartition plate 264 of the deposition chamber 216 can be reduced furtherin volume ratio with respect to the flow rate of the annealing gas. Theannealing gas can thus be supplied more efficiently. When thermalannealing is performed in this state, the Si wafer 206 can be heatedeven more rapidly since it lies closer to the RTP unit 202.

Now, in order to cool the Si wafer 206 after the annealing, the movingmechanism 212 is adjusted to position the Si wafer 206 below the inletof the purge gas as shown in FIG. 11. Here, the annealing gas outlet 266arranged in the upper part of the deposition chamber 216 and the outletformed in the lower part of the deposition chamber 216 both are used forexhaust. The cooling can thus be performed even more efficiently. Thismakes it possible to lower the temperature more sharply.

Incidentally, while the deposition system 262 is configured so that thesides of the partition plate 264 come into contact with the sides of theSi wafer 206 or the sides of the stage 268, there may be a predeterminedclearance.

Fourth Embodiment

The process management in the foregoing embodiments may be conducted,for example, in the following manner. FIG. 15 is a diagram forexplaining a method of process management in the foregoing depositionsystems.

In FIG. 15, a process management unit 270 exercises schedule managementon each individual process based on time information input from aclocking unit 272. This schedule management will now be described alongthe flowchart of FIG. 5, assuming the case of the deposition system 260described in the second embodiment. A source gas control unit 276controls the amount of the source gas to be supplied from the source gassupply pipe 222 (S101). Here, the temperature of the heater 208 in thedeposition process is controlled by a heater control unit 286. At thestage when the source gas has been supplied from the source gas supplypipe 222 for a certain period of time, the source gas control unit 276stops the supply of the source gas. An exhaust control unit 288 makesthe deposition chamber 216 exhausted through the outlet (S102) After alapse of a predetermined time, the exhaust is stopped.

Next, the reactive gas is supplied from the reactive gas supply pipe 226for a predetermined time (S103). The supply of the reactive gas iscontrolled by a reactive gas control unit 278. After the reactive gashas been supplied for the certain period of time, the reactive gascontrol unit 278 stops the supply of the reactive gas. The exhaustcontrol unit 288 makes the deposition chamber 216 exhausted (S104).After a lapse of a predetermined time, the exhaust is stopped.

Then, a moving mechanism control unit 274 operates the moving mechanism212 for a predetermined time, so that the Si wafer 206 approaches theRTP unit 202. An RTP control unit 284 makes the RTP unit 202 startheating. An annealing gas control unit 280 supplies the annealing gasfrom the annealing gas supply pipe 218 to the deposition chamber 216 fora certain period of time (S105). After a lapse of a predetermined time,the heating of the RTP unit 202 and the supply of the annealing gas arestopped. A purge gas control unit 282 starts supplying the purge gasfrom the purge gas supply pipe 230, and the exhaust control unit 288starts exhausting air from the outlet. The operations described aboveare repeated until a predetermined time. When the predetermined time haselapsed (Yes at S107), film refining processing is performed as in S105,thereby completing deposition.

The foregoing sequences are managed by the process management unit. Thesequences shown in FIG. 7 can also be performed based on the method ofthe present embodiment.

Incidentally, the process management shown in FIG. 15 may be scheduledsuch that the annealing gas is supplied at predetermined timing afterthe start of the heating by the RTP unit 202.

Fifth Embodiment

The process management described in the fourth embodiment may also beexercised, for example, in the following manner. FIG. 16 is a diagramfor explaining another method of process management in the foregoingdeposition systems.

In FIG. 16, while the moving mechanism control unit 274 controls theoperation of the moving mechanism 212, it also controls the operationsof the annealing gas control unit 280 and the RTP control unit 284 basedon the position of the Si wafer 206 sensed by a substrate positionsensing unit 290. Consequently, when the Si wafer 206 is moved to apredetermined position, the RTP control unit 284 makes the RTP unit 202start heating, and the annealing gas control unit 280 starts the supplyfrom the annealing gas supply pipe 218. Here, the supply of theannealing gas may be scheduled so as to be started after a predeterminedtime since the heating of the RTP unit 202.

This makes it possible to perform deposition and thermal annealing witheven higher reliability, thereby obtaining a film of favorable qualitystably. The sequences shown in FIG. 7 may also be performed based on themethod of the present embodiment.

Sixth Embodiment

The present embodiment relates to anther example of the depositionmethod that uses the deposition system 260 described in the secondembodiment (FIGS. 8 and 9). The present embodiment will deal with anexample where annealing is performed in an atmosphere containing anitrogen compound gas so that nitrogen is diffused into a metal compoundlayer. The RTP unit 202 shall be an infrared lamp.

Hereinafter, description will be given of the case where Al₂O₃ and AlONare layered in this order on a silicon substrate by ALD.

FIG. 12 shows the gas supply and the temperature profile in thedeposition process. This profile can be achieved, for example, by themethod described in the fourth embodiment or the fifth embodiment.Initially, trimethyl aluminum (TMA), the source gas, is introduced toform an aluminum atomic layer. Subsequently, the deposition chamber 216is purged inside by using the purge gas. Then, H₂O gas, the reactivegas, is introduced to form an oxygen atomic layer. Both the aluminumatomic layer and the oxygen atomic layer are formed at temperatures ofaround 200° C. to 450° C.

Next, thermal annealing is performed for the sake of impurity removaland film densification. The annealing temperature and time are 600° C.to 1050° C. and 1 to 600 sec, for example. The rate of temperature riseduring annealing is 100° C./sec or higher.

The series of steps describe above are repeated a plurality of times tostack metal oxide layers.

Subsequently, when a predetermined thickness is reached, nitrogenintroduction processing is performed. That is, as shown in FIG. 12, NH₃is supplied during annealing. Consequently, nitrogen is introduced anddiffused into the layer. The annealing conditions here are the same asdescribed above.

In this way, a high dielectric constant thin film having Al₂O₃ and AlONlayered in this order can be formed.

According to the method of the present embodiment, sophisticated controlon the amount of nitrogen to be introduced can be effected by such meansas an adjustment to the annealing conditions. Moreover, a desireddistribution of nitrogen concentration can be formed stably inside thehigh dielectric constant thin film.

When nitrogen is introduced into the metal oxide film, thecrystallization temperature of the film increases for improved filmquality. The chemical stability improves as well. In the meantime, theresulting film has such characteristics as a lower barrier againstelectron and a propensity to trapping electron. Thus, if nitrogen can beintroduced into the metal oxide film with a certain distribution ofnitrogen concentration to form high-nitrogen and low-nitrogen regions,then it becomes possible to achieve excellent device performancepreviously unavailable. Since the method of the present embodimentallows precise control on such a distribution of nitrogen concentration,it can be suitably used for device manufacturing steps.

While the present embodiment uses the deposition system 260, thedeposition systems 200 and 262 may also be used.

Seventh Embodiment

The sixth embodiment has dealt with the case where annealing isperformed each time an atomic layer is formed. In contrast, the presentembodiment adopts a method of performing annealing after a plurality ofatomic layers are stacked.

The present embodiment will deal with the case where Al₂O₃ and AlON arelayered in this order on a silicon substrate by ALD. Here, thedeposition system 260 described in the second embodiment (FIGS. 8 and 9)is used, for example.

FIG. 13 shows the gas supply and the temperature profile in thedeposition process. This profile can be achieved, for example, by themethod described in the fourth embodiment or the fifth embodiment.Initially, trimethyl aluminum (TMA), the source gas, is introduced toform an aluminum atomic layer (step A). The deposition chamber 216 ispurged inside by using the purge gas. Then, H₂O gas, the reactive gas,is introduced to form an oxygen atomic layer (step B). Both aluminum andoxygen are deposited at temperatures of around 150° C. to 450° C.

The foregoing steps A and B are performed for two to five cycles,thereby forming an Al₂O₃ layer.

Next, thermal annealing is performed for the sake of impurity removaland film densification. The annealing temperature and time are 600° C.to 1050° C. and 1 to 600 sec, for example. The rate of temperature riseduring annealing is 100° C./sec or higher (step C).

Subsequently, the foregoing steps A and B are performed for two to fivecycles to form an Al₂O₃ layer, followed by the thermal annealing of stepC. During this annealing, a nitrogen compound gas is introduced into thedeposition chamber (step D). Here, ammonia is introduced. As a result,nitrogen is introduced into the aluminum oxide layer, thereby forming anAlON layer.

A high dielectric constant thin film having Al₂O₃ and AlON layered inthis order can thus be formed by using the process described above.

While the present embodiment uses the deposition system 260, thedeposition systems 200 and 262 may also be used.

In the present embodiment, annealing is performed after the formation ofseveral atomic layers. A high dielectric constant material film offavorable quality can thus be obtained through the simple process.

Up to this point, description has been given of the embodiments of thepresent invention. It will be understood by those skilled in the artthat the foregoing embodiments are given for illustration purpose only,and various modifications may be made thereto. All such modificationsare also intended to fall within the scope of the present invention.

1. A deposition system which supplies a source gas and a purge gasalternately for deposition, comprising: a deposition chamber; asubstrate holding unit which holds a substrate in the depositionchamber; a source gas supply unit which supplies the source gas to thedeposition chamber; a reactive gas supply unit which supplies a reactivegas to the deposition chamber; a purge gas supply unit which suppliesthe purge gas to the deposition chamber; an exhaust unit which exhauststhe source gas, the reactive gas, and the purge gas from the depositionchamber; a first heating unit which heats the substrate arranged in thedeposition chamber to maintain the same to a predetermined temperature;a second heating unit which heats the substrate arranged in thedeposition chamber rapidly; an annealing gas introducing unit whichintroduces an annealing gas into the deposition chamber; and a partitionplate positioned lower than an inlet of the annealing gas introducingunit and higher than inlets of the reactive gas supply unit, the sourcegas supply unit, and the purge gas supply unit, the partition platehaving a single center opening; wherein the first heating unit is aheater formed on a substrate holding surface of the substrate holdingunit; the substrate holding unit has a moving mechanism which moves thesubstrate in position so that the distance between the substrate and thesecond heating unit can be adjusted by an operation from outside thedeposition chamber without opening the deposition chamber, and thesubstrate holding unit and the partition plate are structure such thatthe substrate holding unit contacts the partition plate when thesubstrate holding unit is in a raised position; and the substrateholding unit and the partition plate are structured such that thesubstrate is accessible to the annealing gas through the center openingin the partition plate when the substrate holding unit is in the raisedposition.
 2. The deposition system according to claim 1, wherein thefirst heating unit and the second heating unit are opposed to each otherwith the substrate interposed therebetween, so that the first heatingunit heats the substrate from the backside and the second heating unitheats the substrate from the surface.
 3. The deposition system accordingto claim 1, wherein the second heating unit is an RTP (Rapid ThermalProcessing) unit.
 4. The deposition system according to claim 1, whereinthe second heating unit is arranged outside the deposition chamber. 5.The deposition system according to claim 1, further comprising anannealing gas introducing unit which introduces an annealing gas intothe deposition chamber.
 6. The deposition system according to claim 1,wherein when the substrate is put closer to the second heating unit bythe moving mechanism, the substrate or the substrate holding unitsections the deposition chamber into a first chamber having theannealing gas introducing unit and a second chamber having the sourcegas supply unit and the reactive gas supply unit so that the surface ofthe substrate is exposed to the first chamber.
 7. The deposition systemaccording to claim 1, further comprising a control unit which controlsthe operation of the second heating unit and the moving mechanism, thecontrol unit being configured to start heating the substrate by usingthe second heating unit after the substrate is put closer to the secondheating unit by the moving mechanism.
 8. The deposition system accordingto claim 7, wherein the exhaust unit is also controlled by the controlunit so that it can exhaust air from the entire deposition chamber whenthe substrate is put away from the second heating unit by the movingmechanism.
 9. The deposition system according to claim 1, furthercomprising: a control unit which controls the operation of the secondheating unit, the annealing gas introducing unit, and the movingmechanism, and wherein the control unit starts heating the substrate byusing the second heating unit and introduces the annealing gas to thedeposition chamber from the annealing gas introducing unit when thesubstrate is put closer to the second heating unit by the movingmechanism.